An insertion-type exhaust pipe joint includes an inner pipe and an outer pipe having an inside diameter substantially identical to the outside diameter of this inner pipe, wherein the outer pipe has an enlarged-diameter portion at its pipe end portion, and the inner pipe has a pipe end portion which is passed through the enlarged-diameter portion of the outer pipe and is fitted at its one end portion to the pipe end portion of the outer pipe, and wherein a gasket is fitted in an annular gap between the pipe end portion of the inner pipe and the enlarged-diameter portion of the outer pipe so as to seal the gap between the inner and outer pipes by a tightening band disposed on the outer peripheral surface of the outer pipe (refer to Patent Document 1, Patent Document 2, and Patent Document 3).
Further, as a gasket which is used for the above-described exhaust pipe joint, a gasket has been proposed wherein a strip is formed by cutting an expanded graphite sheet into a fixed width and length, a metal wire net cut to a length substantially identical to the length of the expanded graphite sheet is superposed on this strip, this superposed assembly is convoluted around a cylindrical core with the metal wire net placed on the inner side to fabricate a hollow cylindrical member, and this hollow cylindrical member is inserted in a die and is subjected to compression forming in its axial direction, whereby the metal wire net or the expanded graphite is exposed on its inner peripheral surface and its opposite end faces and outer peripheral surface are covered by the expanded graphite (refer to Patent Document 1 and Patent Document 3).
In addition, there has also been proposed an annular gasket wherein a gasket main body is provided by enclosing overall surfaces of an expanded graphite sheet by a metallic net, and the gasket main body is curved into a an annular shape and is compressed by a press machine such that the expanded graphite and the net are integrally secured to each other (refer to Patent Document 4).
In the expanded graphite which is used in the gasket proposed in the above-described Patent Documents 1 to 3, its characteristics such as heat resistance, chemical resistance, and low-friction property are substantially equivalent to those of normal graphite; however, such expanded graphite can be easily formed into a thin sheet or a block by being subjected to pressurization without using a binder, and an object thus obtained has a characteristic of being pliable and flexible unlike the aforementioned graphite.
Accordingly, the gasket, which is formed of expanded graphite and a metal wire net and is disposed between the inner pipe and an enlarged-diameter portion of the outer pipe of the exhaust pipe joint, undergoes expansion in volume due to the heat of exhaust gases flowing through the inner pipe and has pliability and flexibility, so that the gasket is capable of adapting itself well and fits to the gap between the inner pipe and the outer pipe, thereby making it possible to improve the sealability between the inner pipe and the outer pipe (refer to Patent Document 1).